I. Field of the Invention
The present invention relates to communications systems employing message transmitting stations and Earth orbit relay stations to send messages to mobile vehicles. More specifically, the present invention relates to a novel and improved method and apparatus for utilizing such communications systems to enable efficient assignment of freight hauling vehicles to freight loads within commercial freight transportation systems.
II. Description of the Related Art
A need is recognized by many in the mobile vehicle environment for vehicle location and dispatch messaging capability. One industry in particular in which such information is particularly desirable is the commercial trucking industry. In the commercial trucking industry an efficient and accurate method of vehicle position determination is in demand. With ready access to vehicle location information, the trucking company home base obtains several advantages. The trucking company can keep the customer apprised of location, route and estimated time arrival of payloads. The trucking company can also use vehicle location information together with empirical data on the effectiveness of routing, thereby determining the most economically efficient routing paths and procedures.
As used hereinafter the terms "freight hauling vehicle" and "tractor under load" both refer to a tractor truck, i.e., a "tractor vehicle", to which has been engaged a freight load, i.e., a "load". When the tractor truck and freight load forming a given freight hauling vehicle become disengaged at, for example, a destination or stopover location, the resulting vehicle components will be separately referred to as a "tractor vehicle" and as a "load".
The commercial trucking industry has implemented versatile mobile communication terminals for use in their freight hauling trucks. These terminals are capable of providing two-way communication between the trucking company home base and the truck. Typically the communications are via satellite between the truck and a network communications center or Hub. The trucking company is coupled by conventional means, such as telephone lines, to the Hub.
Using the satellite communication capability at each mobile terminal to provide vehicle position determination offers great advantages to the commercial trucking industry. For example, this capability obviates the need for truck drivers themselves, via telephones, to provide location reports regarding their vehicle position to the trucking company home base. These location reports are intermittent at best, because they occur only when the truck driver has reached a destination or stopover site, and require the expenditure of the driver's time to phone the trucking company home base. This method of location report also leaves room for substantial inaccuracies. For example, truck drivers may report incorrect location information either mistakenly or intentionally; or report inaccurate estimates of times of arrival and departure.
In contrast, the use of satellite communication capability at each truck enables the location trucking company home base to identify the longitude/latitude position of each truck at will, thus avoiding the disadvantages associated with intermittent location reports. For example, the "down time" (i.e., periods of zero revenue production) of idle trucks is minimized since the communications necessary for determining location could take place while trucks are en route. Also, inaccuracies in location reports are virtually eliminated because the trucking company home base is able to ascertain accurate truck location nearly instantaneously.
Although satellite communication systems are well-suited to accurately identify the locations of tractor vehicles and loads, it has heretofore been incumbent upon dispatch operators at the company base station to manually assign individual tractor vehicles to specific loads. In matching tractor vehicles with loads, company dispatch operators typically attempt to minimize the "deadhead" required to be traveled by each tractor vehicle en route to a load rendezvous, or "pick-up", location. The term "deadhead" refers to distance traveled by a tractor vehicle while unencumbered by a trailer load. Deadhead mileage is thus undesirable since it does not generate revenue, yet requires the expenditure of both vehicle and driver resources. Accordingly, at first blush the minimization of deadhead would appear to be a logical criteria to be used by dispatch operators confronted with the task of manually assigning tractor vehicles to loads within a commercial freight transportation system.
However, manual determination of the tractor vehicle assignments resulting in minimum total deadhead mileage is a difficult task even with access to the type of tractor vehicle and trailer position information provided by satellite navigation systems. The process of manual assignment has proven to be particularly complex and time-consuming for relatively large tractor fleets. Moreover, such manual assignment does not easily allow for the modification of existing tractor vehicle assignments based upon the real-time position information provided by satellite navigation systems.
Perhaps more importantly, however, using the minimization of deadhead as the primary criterion in making tractor vehicle assignments will generally not maximize the revenue produced by the tractor fleet. That is, tractor vehicle assignment based on deadhead minimization fails to account for the "down time" during which tractor vehicles remain idle while waiting until an assigned load becomes available. Such "down time" carries with it an opportunity cost equivalent to the revenue which could be produced were the tractor vehicle actually being utilized to deliver a payload. In an effort to minimize deadhead, dispatch operators often delay a tractor vehicle for extended periods of time until a load becomes available at a pick-up location relatively nearby. Unfortunately, dispatch operators are frequently unaware of the opportunity cost (i.e., loss of potential revenue) associated with tractor vehicle down time. Hence, it is clear that the current manual process of determining tractor vehicle assignments on the basis of deadhead information is difficult, and generally will not lead to the most economically efficient matching of tractor vehicles and loads as a consequence of the inadequate consideration given to the opportunity costs associated with idle tractor vehicles.